1. Field of the Invention
This invention relates to a clutch apparatus for vehicles.
2. Description of the Prior Arts
Heretofore, there is known a wet type multiplate clutch for use in vehicles, for example, two-wheeled vehicles (motorcycles). The clutch of this type is constructed as follows. A first friction plate (referred to as clutch plate hereinafter) of the ring form which is movably supported within a tubular outer case in the thrust direction, and a second friction plate (referred to as friction disk hereinafter) which is supported on the outer periphery of a clutch hub penetrating through the center of the clutch plate and which is movable in the thrust direction, are brought into close contact with each other in lubricating oil, so that a rotary shaft coupled to the outer case side is connected with a rotary shaft coupled to the clutch hub side by a friction force generated between both the friction plates. Close contact of one friction plate with the other friction plate is effected by means of a spring compressedly mounted within the outer case. Disengagement therebetween is effected by operating a clutch lever which is connected, through a clutch wire, with a link mechanism adapted to compress the spring.
With such construction, however, an operating force large enough to overcome a reaction force of the spring and allowing both the friction plates to come into close contact is required to operate the clutch lever depending on leverage of the link mechanism interposed in the force transmission route. Stated differently, in case the load of the spring allowing both the friction plates to come into close contact is increased, thereby to enlarge torque capacity of the clutch, operation of the clutch lever requires more force, if leverage of the link mechanism is not increased correspondingly. But leverage of the link mechanism is restricted by various conditions, such as, mounting space in the two-wheeled vehicle, dimension of the components restrained by the mounting space, and strength of the components determined by such limited dimension. The maximum ratio is usually as much as 20 times and it is difficult to select the ratio larger than that from the standpoint of design. Therefore, enlargement of the leverage can offer only a limited controllable range of an operating force for the clutch lever. Thus, when such a clutch is applied to large-sized vehicles having large transmission torque, the diameter and number of friction plates must be increased, while maintaining constant the load of the spring, allowing those friction plates to come into close contact with one another, in order to enlarge the torque capacity with the operating force being small. This results in the size of the entire clutch being large.
Heretofore, there is also known a clutch apparatus wherein a change arm adapted to effect the gear change of a transmission is coupled to a clutch through a cam or link mechanism. The cam or link mechanism is driven with an initial movement amount of the change arm to make engagement and disengagement of the clutch when the change gear is operated. The normal gear shifting operation is performed with the latter movement amount of the change arm.
In such clutch apparatus, the initial amount of movement of the change arm and the operating load necessary for such movement are determined by leverage of the cam or link mechanism to engage and disengage the clutch. However, both factors have the relationship that an increase of one factor results in a decrease of the other factor. A fairly large stroke is required to hold the operating load within a range where the change arm can be readily operated by the hand or foot of the driver. Accordingly, in comparison with the normal transmission mechanism wherein a clutch lever is provided to engage and disengage the clutch independently of a change arm and these arm and lever are operated separately to effect the gear change, in the conventional automatic change clutch the initial amount of movement of the change arm required a relatively large stroke and hence rapid change operation is not secured. Further, as to engines which have a limited crank case width restricting the mounting space for the cam or link mechanism, the conventional automatic change clutch can not be applied to a multistage transmission with more than four stages.